keypad.c

#include "Io.h"
#include "tm4c123gh6pm.h"
#include "keypad.h"		


											

/* Array of 4x4 to define characters which will be printe on specific key pressed */
unsigned  char symbol[RowsSize][ColsSize] =    {{ '1', '2',  '3', 'A'},      
                                                { '4', '5',  '6', 'B'},      
                                                { '7', '8',  '9', 'C'},      
                                                { '*', '0',  '#', 'D'}};

																								
void keypad_Init(void)
{
  SYSCTL_RCGCGPIO_R |= 0x09;            //enable clc for port A & D  
  while ((SYSCTL_RCGCGPIO_R&0x09)==0);  //wait for clock to be enabled
  GPIO_PORTA_CR_R  |= 0xF0;             //allow changes to all the bits in port A
  GPIO_PORTD_CR_R  |= 0x0F;             //allow changes to all the bits in port D
  GPIO_PORTA_DIR_R |= 0xF0;             //set directions cols are o/ps
  GPIO_PORTD_DIR_R |= 0x00;             //set directions raws are i/ps
  GPIO_PORTD_PDR_R |= 0x0F;             //pull down resistor on Raws
  GPIO_PORTA_DEN_R |= 0xF0;             //digital enable pins in port A
  GPIO_PORTD_DEN_R |= 0x0F;             //digital enable pins in port D
	GPIO_PORTD_DATA_R &=0x0F; 
	GPIO_PORTA_DATA_R &= 0xF0; 
							
}

/* keypad_getkey() function returns the value of key pressed by the user by traversing columns
and rows respectivley */
unsigned char keypad_getkey(void)
{
	int j;
	int i;
  while(1)
  {
    
		for(i=0; i < 4; i++)    //Scan columns loop
    {
      GPIO_PORTA_DATA_R = (1U << (i +4));
      delayMs(2);
			
      for( j= 0; j < 4; j++)  //Scan rows
      {
        if((GPIO_PORTD_DATA_R  & 0x0F) & (1U << (j))){
         GPIO_PORTD_DATA_R &= (~0x0F); 
				GPIO_PORTA_DATA_R &= (~0xF0); 
				return symbol[j][i];}
      }
    }
  }
	return 0xFF;
}